Couch wrote on his Twitter account Friday, "I want to apologize to everyone from my family, teammates n the Volnation. I'm sorry I let u guys down."
Although the account (@MoTrilla44) isn't verified, Tennessee athletic department spokesman Jason Yellin confirmed it belongs to Couch.
Tennessee coach Butch Jones said Couch wouldn't play against Oregon as the university investigates allegations he received improper benefits.
Yahoo! Sports reported that Couch, former Alabama offensive tackle D.J. Fluker, former Tennessee quarterback Tyler Bray, former Mississippi State defensive tackle Fletcher Cox and former Mississippi State receiver Chad Bumphis received payments from Luther Davis, who acted as a go-between for the players with agents and financial advisers.
Couch, a senior from Orlando, Fla., was the only active college player named in the report, which said Couch had received four payments totaling $1,350.
Jones wouldn't discuss Couch's status for the rest of the season.
"All I can speak of right now is the present," Jones said during his weekly interview with Nashville radio station 104.5 FM, "and the present is he will not be accompanying us to Oregon."
Couch, 23, played in each of Tennessee's first two games as a reserve and made four tackles and one sack. He had 38 tackles and one sack and started nine games last season.
The Yahoo! Sports report named three NFL agents and three financial advisers who it said engaged in transactions totaling at least $45,550, with Davis' between September 2011 and December 2012. The report said records show Davis distributing at least $12,700 in cash, airfare and other expenses to the five players.
Tennessee issued a statement Wednesday afternoon saying it was looking into the situation.
"The education of our student-athletes regarding NCAA rules and extra benefits is and will continue to be the central focus of our compliance efforts," Tennessee athletic department spokesman Jimmy Stanton said. "We are aware of the article and are examining all of the relevant facts."